This invention relates to olefin polymerization catalysts containing a metal atom bound to at least two group 15 atoms fed in solution or slurry into a gas phase or slurry phase reactor to produce polyolefins and the polyolefins produced therefrom.
Metallocene polymerization catalysts (i.e. transition metals, typically groups 4, 5 or 6, having at least one pi bonded ligand, preferably a cyclopentadienyl, indenyl or fluorenyl group) have recently been used to produce resins having a desirable product properties.
Furthermore, there is always a need in the art for a method to introduce catalysts into a gas or slurry phase reactor in such a way as to reduce fouling and/or increase activity. Catalysts used in the gas phase are typically supported because in the past liquid catalysts severely fouled the reactor. Some supported catalysts however have the disadvantages of reduced activity. Thus there is a need in the art of gas or slurry phase processes to find efficient, cost effective reduced fouling means to feed catalysts into a gas or slurry phase reactor. For more information on the disadvantages of using liquid catalysts in a gas phase reactor see the background sections of U.S. Pat. No. 5,317,036 and U.S. Pat. No. 5,693,727 which relates to introducing unsupported catalysts into a gas phase reactor.
Schrock et al in U.S. Pat. No. 5, 889,128 discloses a process for the living polymerization of olefins in solution using initiators having a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. In particular, the solution phase polymerization of ethylene using {[NON]ZrMe}[MeB(C6F5)3] or {[NON]ZrMe(PhNMe2)]}[B(C6F5)4] is disclosed in examples 9 and 10.
Mitsui Chemicals, Inc. in EP 0 893 454 A1 discloses transition metal amides combined with activators to polymerize olefins in the solution phase. EP 893 454 A1 discloses unsupported transition metal amide compounds used in combination with activators to polymerize olefins in the solution phase.
Ethylenebis(salicylideneiminato)zirconium dichloride combined with methyl alumoxane deposited on a support and unsupported versions were used to polymerize ethylene by Repo et al in Macromolecules 1997, 30, 171-175.
U.S. Ser. No. 09/312,878, filed May 17, 1999 discloses novel supported catalysts used in the gas or slurry phase to polymerize olefins.
This invention relates to a catalyst system comprising a liquid carrier, an activator and a metal catalyst compound comprising a group 3 to 14 metal atom bound to at least one anionic leaving group and also bound to at least two group 15 atoms, at least one of which is also bound to a group 15 or 16 atom through another group which may be a C1 to C20 hydrocarbon group, a heteroatom containing group, silicon, germanium, tin, lead, phosphorus, or a halogen, wherein the group 15 or 16 atom may also be bound to nothing or a hydrogen, a group 14 atom containing group, a halogen, or a heteroatom containing group, and wherein each of the two group 15 atoms are also bound to a cyclic group and may optionally be bound to hydrogen, a halogen, a heteroatom or a hydrocarbyl group, or a heteroatom containing group.
This invention relates to the gas or slurry phase polymerization of olefins using an olefin polymerization catalyst system comprising an activator, a liquid carrier and a transition metal compound as described below.
The activator is preferably an aluminum alkyl, an alumoxane, a modified alumoxane, a non-coordinating anion, a borane, a borate or a combination thereof.
The carrier is preferably an alkane.
In a preferred embodiment the activator is combined with a compound represented by the formulae: 
wherein
M is a Group 3 to 12 transition metal or a Group 13 or 14 main group metal, preferably a Group 4, 5, or 6 metal, and more preferably a Group 4 metal, and most preferably zirconium, titanium or hafnium,
each X is independently a leaving group, preferably, an anionic leaving group, and more preferably hydrogen, a hydrocarbyl group, a heteroatom or a halogen, and most preferably an alkyl.
y is 0 or 1 (when y is 0 group Lxe2x80x2 is absent),
n is the oxidation state of M, preferably +3, +4, or +5, and more preferably +4,
m is the formal charge of the YZL or the YZLxe2x80x2 ligand, preferably 0, xe2x88x921, xe2x88x922 or xe2x88x923, and more preferably xe2x88x922,
L is a Group 15 or 16 element, preferably nitrogen,
Lxe2x80x2 is a Group 15 or 16 element or Group 14 containing group, preferably carbon, silicon or germanium,
Y is a Group 15 element, preferably nitrogen or phosphorus, and more preferably nitrogen,
Z is a Group 15 element, preferably nitrogen or phosphorus, and more preferably nitrogen,
R1 and R2 are independently a C1 to C20 hydrocarbon group, a heteroatom containing group having up to twenty carbon atoms, silicon, germanium, tin, lead, or phosphorus, preferably a C2 to C20 alkyl, aryl or aralkyl group, more preferably a linear, branched or cyclic C2 to C20 alkyl group, most preferably a C2 to C6 hydrocarbon group.
R3 is absent or a hydrocarbon group, hydrogen, a halogen, a heteroatom containing group, preferably a linear, cyclic or branched alkyl group having 1 to 20 carbon atoms, more preferably R3 is absent, hydrogen or an alkyl group, and most preferably hydrogen
R4 and R5 are independently an alkyl group, an aryl group, substituted aryl group, a cyclic alkyl group, a substituted cyclic alkyl group, a cyclic aralkyl group, a substituted cyclic aralkyl group or multiple ring system, preferably having up to 20 carbon atoms, more preferably between 3 and 10 carbon atoms, and even more preferably a C1 to C20 hydrocarbon group, a C1 to C20 aryl group or a C1 to C20 aralkyl group, or a heteroatom containing group, for example PR3, where R is an alkyl group,
R1 and R2 may be interconnected to each other, and/or R4 and R5 may be interconnected to each other,
R6 and R7 are independently absent, or hydrogen, an alkyl group, halogen, heteroatom or a hydrocarbyl group, preferably a linear, cyclic or branched alkyl group having 1 to 20 carbon atoms, more preferably absent, and
R* is absent, or is hydrogen, a Group 14 atom containing group, a halogen, a heteroatom containing group.
By xe2x80x9cformal charge of the YZL or YZLxe2x80x2 ligandxe2x80x9d, it is meant the charge of the entire ligand absent the metal and the leaving groups X.
By xe2x80x9cR1 and R2 may also be interconnectedxe2x80x9d it is meant that R1 and R2 may be directly bound to each other or may be bound to each other through other groups. By xe2x80x9cR4 and R5 may also be interconnectedxe2x80x9d it is meant that R4 and R5 may be directly bound to each other or may be bound to each other through other groups.
An alkyl group may be a linear, branched alkyl radicals, or alkenyl radicals, alkynyl radicals, cycloalkyl radicals or aryl radicals, acyl radicals, aroyl radicals, alkoxy radicals, aryloxy radicals, alkylthio radicals, dialkylamino radicals, alkoxycarbonyl radicals, aryloxycarbonyl radicals, carbomoyl radicals, alkyl- or dialkyl-carbamoyl radicals, acyloxy radicals, acylamino radicals, aroylamino radicals, straight, branched or cyclic, alkylene radicals, or combination thereof. An aralkyl group is defined to be a substituted aryl group.
In a preferred embodiment, L is bound to one of Y or Z and one of R1 or R2 is bound to L and not to Y or Z.
In an alternate embodiment R3 and L do not form a heterocyclic ring.
In a preferred embodiment R4 and R5 are independently a group represented by the following formula: 
wherein
R8 to R12 are each independently hydrogen, a C1 to C40 alkyl group, a heteroatom, a heteroatom containing group containing up to 40 carbon atoms, preferably a C1 to C20 linear or branched alkyl group, preferably a methyl, ethyl, propyl or butyl group, any two R groups may form a cyclic group and/or a heterocyclic group. The cyclic groups may be aromatic. In a preferred embodiment R9, R10 and R12 are independently a methyl, ethyl, propyl or butyl group, in a preferred embodiment R9, R10 and R12 are methyl groups, and R8 and R11 are hydrogen.
In a particularly preferred embodiment R4 and R5 are both a group represented by the following formula: 
These metal compounds are prepared by methods known in the art, such as those disclosed in EP 0 893 454 A1 and U.S. Pat. No. 5,889,128 and the references cited therein which are all incorporated by reference herein. A preferred direct synthesis of these compounds comprises reacting the neutral ligand with MnXn (M is a group 3-14 metal, n is the oxidation state of M, X is an anionic group, such as halide, in a non-coordinating or weakly coordinating solvent, such as ether, toluene, xylene, benzene, methylene chloride, and/or hexane or other solvent having a boiling point above 60xc2x0 C., at about 20 to about 150xc2x0 C. (preferably 20 to 100xc2x0 C.), preferably for 24 hours or more, then treating the mixture with an excess (such as four equivalents) of an alkylating agent, such as methyl magnesium bromide in ether. The magnesium salts are removed by filtration, and the metal complex isolated by standard techniques.
In a preferred embodiment this invention relates to a method to prepare a metal compound comprising reacting a neutral ligand with a compound represented by the formula MnXn (where M is a group 3-14 metal, n is the oxidation state of M, X is an anionic leaving group) in a non-coordinating or weakly coordinating solvent, at about 20xc2x0 C. or above, preferably at about 20 to about 100xc2x0 C., then treating the mixture with an excess of an alkylating agent, then recovering the metal complex. In a preferred embodiment the solvent has a boiling point above 60xc2x0 C., such as ether, toluene, xylene, benzene, methylene chloride and/or hexane.
The transition metal compounds described herein are preferably combined with one or more activators to form an olefin polymerization catalyst system. Preferred activators include alkyl aluminum compounds (such as diethylaluminum chloride), alumoxanes, modified alumoxanes, non-coordinating anions, boranes, borates and the like. It is within the scope of this invention to use alumoxane or modified alumoxane as an activator, and/or to also use ionizing activators, neutral or ionic, such as tri (n-butyl) ammonium tetrakis (pentafluorophenyl) boron or a trisperfluorophenyl boron metalloid precursor which ionize the neutral metallocene compound. Other useful compounds include triphenyl boron, triethyl boron, tri-n-butyl ammonium tetraethylborate, triaryl borane and the like.
There are a variety of methods for preparing alumoxane and modified alumoxanes, non-limiting examples of which are described in U.S. Pat. Nos. 4,665,208, 4,952,540, 5,091,352, 5,206,199, 5,204,419, 4,874,734, 4,924,018, 4,908,463, 4,968,827, 5,308,815, 5,329,032, 5,248,801, 5,235,081, 5,157,137, 5,103,031, 5,391,793, 5,391,529, 5,693,838, 5,731,253, 5,041,584 and 5,731,451 and European publications EP-A-0 561 476, EP-B1-0 279 586 and EP-A-0 594-218, and PCT publication WO 94/10180, all of which are herein fully incorporated by reference.
Ionizing compounds may contain an active proton, or some other cation associated with but not coordinated to or only loosely coordinated to the remaining ion of the ionizing compound. Such compounds and the like are described in European publications EP-A-0 570 982, EP-A-0 520 732, EP-A-0 495 375, EP-A-0 426 637, EP-A-500 944, EP-A-0 277 003 and EP-A-0 277 004, and U.S. Pat. Nos. 5,153,157, 5,198,401, 5,066,741, 5,206,197, 5,241,025, 5,387,568, 5,384,299 and 5,502,124 and U.S. patent application Ser. No. 08/285,380, filed Aug. 3, 1994, all of which are herein fully incorporated by reference. Other activators include those described in PCT publication WO 98/07515 such as tris (2,2xe2x80x2,2xe2x80x3-nonafluorobiphenyl) fluoroaluminate, which is fully incorporated herein by reference. Combinations of activators are also contemplated by the invention, for example, alumoxanes and ionizing activators in combinations, see for example, PCT publications WO 94/07928 and WO 95/14044 and U.S. Pat. Nos. 5,153,157 and 5,453,410 all of which are herein fully incorporated by reference. Also, methods of activation such as using radiation and the like are also contemplated as activators for the purposes of this invention.
In general the metal compound and the activator are combined in ratios of about 1000:1 to about 0.5:1. In a preferred embodiment the metal compound and the activator are combined in a ratio of about 300:1 to about 1:1, preferably about 10:1 to about 1:1, for boranes the ratio is preferably about 1:1 to about 10:1 and for alkyl aluminum compounds (such as diethylaluminum chloride combined with water) the ratio is preferably about 0.5:1 to about 10:1.
The metal compound and activator are introduced into a slurry or gas phase reactor in a liquid carrier, preferably in solution. The catalyst and the activator may be fed in separately or together and may be combined immediately before being placed in the reactor or may be contacted for longer periods before being placed in the reactor. Preferred liquid carriers include alkanes, preferably pentane, hexane, isopentane, toluene, cyclohexane, isopentane, heptane, octane, isohexane and the like. Particularly preferred carriers include hexane, pentane, isopentane and toluene.
The catalyst system, the metal compounds and or the activator are preferably introduced into the reactor in one or more solutions. In one embodiment a solution of the activated metal compounds in an alkane such as pentane, hexane, toluene, isopentane or the like is introduced into a gas phase or slurry phase reactor. In another embodiment the catalyst system or the components can be introduced into the reactor in a suspension or an emulsion. In one embodiment, the transition metal compound is contacted with the activator, such as modified methylalumoxane, in a solvent and just before the solution is fed into a gas or slurry phase reactor. In another embodiment a solution of the metal compound is combined with a solution of the activator, allowed to react for a period of time then introduced into the reactor. In a preferred embodiment, the catalyst and activator are allowed to reactor for at least 1 second, preferably at least 5 minutes even more preferably between 5 and 60 minutes, before being introduced into the reactor. The catalyst and activator are typically present at a concentration of 0.0001 to 0.200 mol/l in the solutions, preferably 0.001 to 0.05 mol/l, more preferably 0.005 to 0.025 mol/l.
In a preferred embodiment, the catalyst system consists of the transition metal compound (catalyst) and or the activator (cocatalyst) which are preferably introduced into the reactor in solution. Solutions of the metal compounds are prepared by taking the catalyst and dissolving it in any solvent such as an alkane, toluene, xylene, etc. The solvent may first be purified in order to remove any poisons which may affect the catalyst activity, including any trace water and/or oxygenated compounds. Purification of the solvent may be accomplished by using activated alumina and activated supported copper catalyst, for example. The catalyst is preferably completely dissolved into the solution to form a homogeneous solution. Both catalyst and the activator may be dissolved into the same solvent, if desired. Once the catalysts are in solution, they may be stored indefinitely until use.
For polymerization, it preferred that the catalyst is combined with an activator prior to injection into the reactor. Additionally, other solvents and reactants can be added to the catalyst solutions (on-line or off-line), to the activator (on-line or off-line), or to the activated catalyst or catalysts.
In a preferred embodiment the catalyst systems of this invention have a productivity of 10,000 grams of polymer per gram of catalyst per hour or more,
Polymerization Process of the Invention:
The catalysts and catalyst systems described above are suitable for use in the polymerization process of the invention. The polymerization process of the invention includes a gas phase or slurry phase process or a combination thereof.
In an embodiment, this invention is directed toward the slurry or gas phase polymerization or copolymerization reactions involving the polymerization of one or more monomers having from 2 to 30 carbon atoms, preferably 2-12 carbon atoms, and more preferably 2 to 8 carbon atoms. The invention is particularly well suited to the copolymerization reactions involving the polymerization of one or more olefin monomers of ethylene, propylene, butene-1, pentene-1,4-methyl-pentene-1, hexene-1, octene-1, decene-1,3-methyl-pentene-1,3,5,5-trimethyl-hexene-1 and cyclic olefins or a combination thereof. Other monomers can include vinyl monomers, diolefins such as dienes, polyenes, norbornene, norbornadiene monomers. Preferably a copolymer of ethylene is produced, where the comonomer is at least one alpha-olefin having from 4 to 15 carbon atoms, preferably from 4 to 12 carbon atoms, more preferably from 4 to 8 carbon atoms and most preferably from 4 to 7 carbon atoms.
In another embodiment ethylene or propylene is polymerized with at least two different comonomers to form a terpolymer. The preferred comonomers are a combination of alpha-olefin monomers having 4 to 10 carbon atoms, more preferably 4 to 8 carbon atoms, optionally with at least one diene monomer. The preferred terpolymers include the combinations such as ethylene/butene-1/hexene-1, ethylene/propylene/butene-1, propylene/ethylene/hexene-1, ethylene/propylene/norbornene and the like.
In a particularly preferred embodiment the process of the invention relates to the polymerization of ethylene and at least one comonomer having from 3 to 8 carbon atoms, preferably 4 to 7 carbon atoms. Particularly preferred comonomers are butene-1, 4-methyl-pentene-1, hexene-1 and octene-1, the most preferred being hexene-1 and/or butene-1.
Typically in a gas phase polymerization process a continuous cycle is employed where in one part of the cycle of a reactor system, a cycling gas stream, otherwise known as a recycle stream or fluidizing medium, is heated in the reactor by the heat of polymerization. This heat is removed from the recycle composition in another part of the cycle by a cooling system external to the reactor. Generally, in a gas fluidized bed process for producing polymers, a gaseous stream containing one or more monomers is continuously cycled through a fluidized bed in the presence of a catalyst under reactive conditions. The gaseous stream is withdrawn from the fluidized bed and recycled back into the reactor. Simultaneously, polymer product is withdrawn from the reactor and fresh monomer is added to replace the polymerized monomer. (See for example U.S. Pat. Nos. 4,543,399, 4,588,790, 5,028,670, 5,317,036, 5,352,749, 5,405,922, 5,436,304, 5,453,471, 5,462,999, 5,616,661 and 5,668,228 all of which are fully incorporated herein by reference.)
The reactor pressure in a gas phase process may vary from about 10 psig (69 kPa) to about 500 psig (3448 kPa), preferably in the range of from about 100 psig (690 kPa) to about 400 psig (2759 kPa), preferably in the range of from about 200 psig (1379 kPa) to about 400 psig (2759 kPa), more preferably in the range of from about 250 psig (1724 kPa) to about 350 psig (2414 kPa).
The reactor temperature in the gas phase process may vary from about 30xc2x0 C. to about 120xc2x0 C., preferably from about 60xc2x0 C. to about 115xc2x0 C., more preferably in the range of from about 70xc2x0 C. to 110xc2x0 C., and most preferably in the range of from about 70xc2x0 C. to about 95xc2x0 C.
The productivity of the catalyst or catalyst system is influenced by the main monomer partial pressure. The preferred mole percent of the main monomer, ethylene or propylene, preferably ethylene, is from about 25 to 90 mole percent and the monomer partial pressure is in the range of from about 75 psia (517 kPa) to about 300 psia (2069 kPa), which are typical conditions in a gas phase polymerization process.
In a preferred embodiment, the reactor utilized in the present invention and the process of the invention produce greater than 500 lbs of polymer per hour (227 Kg/hr) to about 200,000 lbs/hr (90,900 Kg/hr) or higher of polymer, preferably greater than 1000 lbs/hr (455 Kg/hr), more preferably greater than 10,000 lbs/hr (4540 Kg/hr), even more preferably greater than 25,000 lbs/hr (11,300 Kg/hr), still more preferably greater than 35,000 lbs/hr (15,900 Kg/hr), still even more preferably greater than 50,000 lbs/hr (22,700 Kg/hr) and most preferably greater than 65,000 lbs/hr (29,000 Kg/hr) to greater than 100,000 lbs/hr (45,500 Kg/hr).
Other gas phase processes contemplated by the process of the invention include those described in U.S. Pat. Nos. 5,627,242, 5,665,818 and 5,677,375, and European publications EP-A-0 794 200, EP-A-0 802 202 and EP-B-634 421 all of which are herein fully incorporated by reference.
A slurry polymerization process generally uses pressures in the range of from about 1 to about 50 atmospheres and even greater and temperatures in the range of 0xc2x0 C. to about 120xc2x0 C. In a slurry polymerization, a suspension of solid, particulate polymer is formed in a liquid polymerization diluent medium to which ethylene and comonomers and often hydrogen along with catalyst are added. The suspension including diluent is intermittently or continuously removed from the reactor where the volatile components are separated from the polymer and recycled, optionally after a distillation, to the reactor. The liquid diluent employed in the polymerization medium is typically an alkane having from 3 to 7 carbon atoms, preferably a branched alkane. The medium employed should be liquid under the conditions of polymerization and relatively inert. When a propane medium is used the process must be operated above the reaction diluent critical temperature and pressure. Preferably, a hexane or an isobutane medium is employed.
In one embodiment, a preferred polymerization technique of the invention is referred to as a particle form polymerization, or a slurry process where the temperature is kept below the temperature at which the polymer goes into solution. Such technique is well known in the art, and described in for instance U.S. Pat. No. 3,248,179 which is fully incorporated herein by reference. The preferred temperature in the particle form process is within the range of about 185xc2x0 F. (85xc2x0 C.) to about 230xc2x0 F. (110xc2x0 C.). Two preferred polymerization methods for the slurry process are those employing a loop reactor and those utilizing a plurality of stirred reactors in series, parallel, or combinations thereof. Non-limiting examples of slurry processes include continuous loop or stirred tank processes. Also, other examples of slurry processes are described in U.S. Pat. No. 4,613,484, which is herein fully incorporated by reference.
In another embodiment, the slurry process is carried out continuously in a loop reactor. The catalyst, typically a slurry in isobutane or a solution in an alkane, is injected regularly to the reactor loop, which is itself filled with circulating slurry of growing polymer particles in a diluent of isobutane containing monomer and comonomer. Hydrogen, optionally, may be added as a molecular weight control. The reactor is maintained at pressure of about 525 psig to 625 psig (3620 kPa to 4309 kPa) and at a temperature in the range of about 140xc2x0 F. to about 220xc2x0 F. (about 60xc2x0 C. to about 104xc2x0 C.) depending on the desired polymer density. Reaction heat is removed through the loop wall since much of the reactor is in the form of a double-jacketed pipe. The slurry is allowed to exit the reactor at regular intervals or continuously to a heated low pressure flash vessel, rotary dryer and a nitrogen purge column in sequence for removal of the isobutane diluent and all unreacted monomer and comonomers. The resulting hydrocarbon free powder is then compounded for use in various applications.
In an embodiment the reactor used in the slurry process of the invention is capable of and the process of the invention is producing greater than 2000 lbs of polymer per hour (907 Kg/hr), more preferably greater than 5000 lbs/hr (2268 Kg/hr), and most preferably greater than 10,000 lbs/hr (4540 Kg/hr). In another embodiment the slurry reactor used in the process of the invention is producing greater than 15,000 lbs of polymer per hour (6804 Kg/hr), preferably greater than 25,000 lbs/hr (11,340 Kg/hr) to about 100,000 lbs/hr (45,500 Kg/hr).
In another embodiment in the slurry process of the invention the total reactor pressure is in the range of from 400 psig (2758 kPa) to 800 psig (5516 kPa), preferably 450 psig (3103 kPa) to about 700 psig (4827 kPa), more preferably 500 psig (3448 kPa) to about 650 psig (4482 kPa), most preferably from about 525 psig (3620 kPa) to 625 psig (4309 kPa).
In yet another embodiment in the slurry process of the invention the concentration of ethylene in the reactor liquid medium is in the range of from about 1 to 10 weight percent, preferably from about 2 to about 7 weight percent, more preferably from about 2.5 to about 6 weight percent, most preferably from about 3 to about 6 weight percent.
A preferred process of the invention is where the process, preferably a slurry or gas phase process is operated in the absence of or essentially free of any scavengers, such as triethylaluminum, trimethylaluminum, tri-isobutylaluminum and tri-n-hexylaluminum and diethyl aluminum chloride, dibutyl zinc and the like. This preferred process is described in PCT publication WO 96/08520 and U.S. Pat. No. 5,712,352, which are herein fully incorporated by reference.
In another preferred embodiment the one or all of the catalysts and/or activators are combined with up to 10 weight % of a metal stearate, (preferably a aluminum stearate, more preferably aluminum distearate) based upon the weight of the catalyst and the stearate, preferably 2 to 3 weight %. In an alternate embodiment a solution of the metal stearate is fed into the reactor. In another embodiment the metal stearate is mixed with the catalyst and fed into the reactor separately. These agents may be mixed with the catalyst or may be fed into the reactor in a solution with or without the catalyst system or its components. In a particularly preferred embodiment a slurry of the stearate in mineral oil is introduced into the reactor separately from the metal compounds and or the activators.
More information on using aluminum stearate type additives may be found in U.S. Ser. No. 09/113,261 filed Jul. 10, 1998, which is incorporated by reference herein.
The catalyst system of this invention has excellent operability over a wide range of reactor conditions and resin grades from 0.2 Flow Index to 3 Melt Index and 0.950 g/cc to 0.916 g/cc density. The catalyst system did not experience any resin agglomeration or sheeting in over 10 days of continuous pilot scale operation. This invention also has the benefit of little or no fouling. No sheets, chunks or rubble were observed during or after the polymerization process. There was no trace of polymer build-up on the inside of the reactor walls or in the recycle gas line. Also, there was no increase in the pressure drop across the heat exchanger, cycle gas compressor or gas distribution plate during the entire run.
In a preferred embodiment, the polyolefin recovered typically has a melt index as measured by ASTM D-1238, Condition E, at 190xc2x0 C. of 3000 g/10 min or less, preferably 1000 g/10 min or less, more preferably 20 g/10 min or less, more preferably 10 g/l 0 min or less. In a preferred embodiment the polyolefin is ethylene homopolymer or copolymer. In a preferred embodiment for certain applications, such as films, molded article and the like a melt index of 100 g/10 min or less is preferred. For some films and molded article a melt index of 10 g/10 min or less is preferred. Polyethylene having a melt index of between 0.01 to 10 dg/min is preferably produced. In another preferred embodiment the polymer produced has a weight average molecular weight of 40,000 Daltons or more, preferably 60,000 or more, preferably 100,000 or more, preferably 120,000 or more, preferably 150,000 or more. For LLDPE cast grade films a weight average molecular weight of 40,000 or more is preferred while a weight average molecular weight of 60,000 or more is preferred for blown film grades.
In another embodiment the polymer produced herein has a composition distribution breadth index (CDBI) of 70 or more, preferably 75 or more even more preferably 80 or more. Composition distribution breadth index is a means of measuring the distribution of comonomer between polymer chains in a given sample. CDBI is measured according to the procedure in WO 93/03093, published Feb. 18, 1993, provided that fractions having a molecular weight below 10,000 Mn are ignored for the calculation.
In a preferred embodiment the catalyst system described above is used to make a polyolefins, preferably polyethylene having a density of between 0.88 and 0.970 g/cm3 (as measured by ASTM 2839). In some embodiments, a density of 0.915 to 0.940 g/cm3 would be preferred, in other embodiments densities of 0.930 to 0.960 g/cm3 are preferred. In particular polyethylenes having a density of 0.910 to 0.965, preferably 0.915 to 0.960, preferably 0.920 to 0.955 can be produced. In some embodiments, a density of 0.915 to 0.940 g/cm3 would be preferred, in other embodiments densities of 0.930 to 0.970 g/cm3 are preferred.
In a particularly preferred embodiment the catalyst system described above is used to make a polyethylene having a density (as measured by ASTM D 1505) of 0.910 to 0.935 g/cm3,(preferably 0.915 to 0.930 g/cm3), and a melt index (as measured by ASTM D-1238, Condition E, at 190xc2x0 C.) of 10 or less dg/min, (preferably 5 dg/min or less even more preferably 3 dg/min or less), giving a film having a haze (as measured by ASTM 1003-95, Condition A) of 10% or less (preferably 7% or less, even more preferably a 5% or less), and a 450 gloss (as measured by ASTM D 2457) of 60 or more, (preferably 75 or more, more preferably 80 or more). In an even more preferred embodiment, the polymer is formed into a film of 0.5 to 10 mil (13 to 250 xcexcm) that has a dart impact (as measured by ASTM D 1709, Method A) of 150 g or more, preferably 200 g or more and an Elmendorf machine direction tear resistance (as measured by ASTM D 1922) of 100 g or more preferably 250 g or more, and an Elmendorf transverse direction tear (as measured by ASTM D 1922) of 500 g or more, preferably 600 g or more.
The polyolefins then can be made into films, molded articles, sheets, pipes, wire and cable coating and the like. The films may be formed by any of the conventional techniques known in the art including extrusion, co-extrusion, lamination, blowing and casting. The film may be obtained by the flat film or tubular process which may be followed by orientation in an uniaxial direction or in two mutually perpendicular directions in the plane of the film to the same or different extents. Orientation may be to the same extent in both directions or may be to different extents. Particularly preferred methods to form the polymers into films include extrusion or coextrusion on a blown or cast film line.
The films produced may further contain additives such as slip, antiblock, antioxidants, pigments, fillers, antifog, UV stabilizers, antistats, polymer processing aids, neutralizers, lubricants, surfactants, pigments, dyes and nucleating agents. Preferred additives include silicon dioxide, synthetic silica, titanium dioxide, polydimethylsiloxane, calcium carbonate, metal stearates, calcium stearate, zinc stearate, talc, BaSO4, diatomaceous earth, wax, carbon black, flame retarding additives, low molecular weight resins, hydrocarbon resins, glass beads and the like. The additives may be present in the typically effective amounts well known in the art, such as 0.001 weight % to 10 weight %.